As the size of pixel in the image sensor is shrinking, crosstalk noise becomes more serious and the problem caused by crosstalk noise needs to be solved to achieve better image quality.
There are three types of crosstalk in the image sensor: spectral crosstalk, optical crosstalk, and electrical crosstalk. Spectral crosstalk is caused by misalignment of the color filter (CF) and the corresponding pixel. Optical crosstalk is generated when photons enter the adjacent pixels. Electrical crosstalk is caused by the fact that electrons drift to wrong pixels.
One way to reduce spectral crosstalk and optical crosstalk is to insert a color filter into the structure of the metal grid. In prior art, when a metal grid is formed, a metal grid material is deposited first. Then the deposited metal grid material is dry etched to remove the unnecessary metal grid material. Thus, a metal grid corresponding to the pixel region is formed.
The inventor finds that when the deposited metal grid material is subjected to dry etching, some of the plasma with charges is left in the pixel region. The adverse effect will be put on the performance of the image sensor. In addition, the dry etching may also damage the pixel region, which will also affect the performance of the image sensor.
The disclosed devices and methods are directed to at least partially alleviate one or more problems set forth above and to solve other problems in the art.